Composite flue



March 9', 1937. J. E. wlLD ET AL 2,073,236

' COMPOSITE FLUE Filed Junel I5, 1936 -lg'l- A copper SeZ ATTORNEY Patented Mar. e, ies? UNITED STATES coMPosrr-E FLUE Julius E. Wild, Longmeadow, and Herbert J. Long, Springfield, Mass., assignors to United American Bosch Corporation,

Springfield,

Mass., a corporation of New York Application June 3, 1936, Serial No. 83,226

3 Claims.

This invention relates to water heaters of the type having a storage tank with a flue extending therethrough for 'heating the contents thereof.

Heaters of this type as heretofore used have been of heavy construction due to the fact that the passage of the flue through the heavy boiler heads involved inherent structural weaknesses, f or which compensation has been sought in the use of heavier materials. AlsoI the tanks being of relatively long cylindrical for'm, required flues .of the same length which were subjected to strains proportional to their length. The materials used due to these diiiiculties involved further difficulties in manufacture, especially in welding the fiues to the boiler heads, and accordingly the cost of such heaters has been relatively high in spite of the fact that in other respects they effect certain savings such as elimination oi parts present in side arm type heaters.

It is among the objects of the present invention to overcome the abovementioned diiiiculties and provide a construction which though of light material is structurally strong, and which for thisreason and because of its ease of manufacture will be of low cost.

A further object of this invention is to provide a heater of this type in which all parts exposed to water will be free from corrosion, being of copper, bronze or the like, while the interior portion of the iiue is of heavy material such as steel and provides necessary reenforcement for the lighter parts as well as ample heat absorbing surface.

The above and other objects and features of the invention will be apparent to those skilled in the art .from the following detailed description taken in conjunction with the accompanying drawing, in which:

Fig. 1 is a longitudinal section through the tank and flue of an internal flue type heater constructed in accordance with this invention; and Fig. 2 is a bottom plan view of the central portion thereof.

Referring to the drawing, reference numeral I indicates a tank which is preferably constructed of sheet copper of sufdcient lightness that the same may be stamped in two hemispherical sections 2 and 3. Each of the sections 2 and 3 is provided with an outwardly extending ilange 4, the opposing surfaces of which may be easily joined as by a stitch weld. The two sectionsso combined form a. substantially spherical tank which is inherently strong, permitting the use of light material. The strength of the structure is further augmented by the use of the reenforcing means hereinafter described. A central tube 5 of the same material as the sections 2 and 3 extends axially through the tank and is welded at each end thereof to axially projecting anges 6 and 1 surrounding axial openings in each of the sections 2 and 3. The welding operation at these points is equally as simple as that between the flanges 4, because the wall of the tube 5 is of the same thickness and ot the same material as the walls of the tank. A tube 8 of substantially the same external diameter as the internal diameter of tube 5 is forced into the latter making a very tight t therewith. The tube 8 is of heavy material such as steel tubing and when so inserted reenforces the thinwalled tube 5 and gives rigidity and strength to the entire structure. Fins 9 project radially from and extend longitudinally of the internal surface of the tube 8 to increase the absorption of -heat from the combustion gases passing through the flue, and also to increase the strength and rigidity of said tube. These ns are preferably welded together at a common central juncture.

It will be seen that the above structure provides a tank of light material which is inexpensive of itself and which'may be formed and assembled in a few simple operations. All interior surfaces of the tank are of the same material, thus avoiding contact between metals .of different electrochemical properties in the presence oi' a liquid, and also facilitating the welding operations, while the internal steel tube'gives the entire structure the necessary strength and rigidity.

Having' thus described the invention, what is claimed aspnew is:

1. In a, water heater, a tank having end walls of light sheet metal, a tube of the same material and having the same thickness as said walls extending therethrough and united therewith, and a tube of heavy material extending through said first mentioned tube and having a tight flt therewith for reeniorcing said first mentioned tube and giving strength and rigidity to said tank.

2. In a water heater, a spherical tank having walls of light lsheet metal, a tube of the same material and having the same thickness as said walls extending therethrough and welded-thereto .at each end, a second tube within said ilrst mentioned tube and having a tight rit therewith, and internal iins integral with said second tube for increasing its strength and rigidity. said combined tubes forming a. central reenforcing member and ue for said tank.

3. In a water heater, a tank having side and end walls of light sheet metal, a tube o! the same material and having the same thickness as said walls extending therethrough and united therewith at each end thereof, a second tube within said iirst mentioned tube having a tight nt therewith, and internal ns integral with said second tube for increasing its strength and rigidity, said combined tubes forming a central reenforcing member for said tank.

JULIUB E. WILD. v HERBERT J. LONG. 

